You are here

Radiation Exposure Reduction During CT Guided Spinal Pain Procedures

The following article was written by William P. Dillon, M.D., Elizabeth A. Guillaumin Professor of Radiology, Executive Vice Chair of Radiology, and Chief of the Neuroradiology Section at UCSF.

A radiologist is tasked with making a diagnosis or performing a procedure in a safe manner with aslow a radiation dose as possible. The lowest dose, of course, is zero. This can be achieved by performing only indicated examinations, and utilizing, when appropriate, imaging modalities, such as ultrasound or MRI, that do not require ionizing radiation to form an image. Nevertheless in many situations CT, an X-ray based technique, provides enormous value and benefit to patients. CT saves lives each day, and provides great benefit for guiding therapies. CT is fast, accurate, and a safer environment for using metal instruments and needles. When using CT, our goal is to use as low a radiation dose as possible without compromising accuracy or safety.

For the last several years we have utilized a dedicated CT scanner at the UCSF Precision Spine Center to guide placement of medication adjacent to sensitive structures such as spinal nerves and the epidural spinal space in patients suffering a variety of disorders that cause neck, back or extremity pain. The use of CT to guide treatment results in more precise placement of medication, less pain and discomfort, and better patient outcomes than conventional X-ray techniques. Neuroradiologists at UCSF have challenged themselves to reduce radiation dose as low as possible, using the latest software for CT reconstruction that permits lower doses of radiation to create images of diagnostic quality. Adaptive statistical iterative reconstruction (ASIR) is a new advance in CT image reconstruction that reduces the noise in an image and improves low contrast detection of structures, thus improving image quality at lower levels of radiation exposure. ASIR was introduced at UCSF in early 2011 and has resulted in radiation dose reductions of up to 40%.

In a recent article in the American Journal of Neuroradiology, “Reducing Patient Radiation Dose during CT-Guided Procedures: Demonstration in Spinal Injections for Pain”, Shepherd et al from UCSF reported that radiation dose to patients undergoing CT-guided spinal injections could be decreased up to 80% without affecting outcome. This is possible by reducing tube current, using axial acquisitions for short scan lengths, and eliminating nonessential imaging guidance. During these procedures, the treating radiologist informs the technologist at the operator console when dose can be reduced for simple guidance and when increased dose is needed for more diagnostic quality scans. This interaction, combined with a goal to reduce radiation dose to the lowest level possible, has had the desired result, with radiation dose levels during CT guided procedures reduced to the equivalent of fluoroscopically guided procedures in many instances. This allows the radiologist to more precisely see the anatomy and pathology that needs treatment at doses comparable to conventional fluoroscopic (X-ray) based techniques. CT allows us to see the nerves, arteries, disc protrusions, and spinal epidural anatomy better than on fluoroscopy, but with the same radiation exposure.

The goal in all of these efforts is to help patients get back to a more normal, useful, quality life. Our procedures may not only assist in pain management, but also be used to document where the pain generator is coming from in the event surgery is required. Many times in less severe cases, proper precise injections may help obviate surgery altogether.